I'll step up to the plate on this one, too.
Stephen, I will tell you that I'm very fortunate in that I've been known to get some features on my stuff, too ... and I have to tell you, I used to spend quite a bit of time ... a lot of time ... saying thank you to group hosts and logging in the features right on each image every day. I did this for years. But ... life gets in the way ... and it all got away from me about a year or two ago (had some personal things happen that weren't very nice and a LOT of things got away from me during that time). So ... I've had to give up this practice ... to the detriment of myself, too, as only 3 feature notices remain on our images now (I think it used to be that all of them, with a link back to the featuring group, were included ... but I might be wrong). So ... by not thanking the hosts and including the group name, I'm hurting myself, possibly, in the eyes of potential purchasers.
As to what you may also be saying, which is adding a thank you to the host of each group in a discussion thread, a great many of the hosts have repeatedly asked that we not do this.
Since I'm in roughly 340 groups, it would be pretty hard to remember which groups don't want thank-yous in their discussion threads, and which do.
And by the way, this goes for our group hosts who go on vacation or whatever and ask us not to submit while they're gone. I'm so sorry .. I know I've really stepped on some toes in that category as well ... so let this be my apology ... but I can't keep up with who's on first, so to speak. I'm gettin' old, lol!!! But also I'd like to take this opportunity to express my most sincere thanks for all that the group hosts do for us. I've never hosted a group, but I have a pretty good imagination, and I can't begin to think that the strum and drang you must go through with some of our members is worth it ... but you guys continue to help us and help promote us ... and I for one truly do appreciate it.
Even if I don't send out a thank you anymore.
Hope this helps you to understand where some of us might be coming from, Stephen.